U.S. patent number 5,009,265 [Application Number 07/404,159] was granted by the patent office on 1991-04-23 for packer for wellhead repair unit.
This patent grant is currently assigned to Drilex Systems, Inc.. Invention is credited to Thomas F. Bailey, Charles E. Lancaster, Richard Lee.
United States Patent |
5,009,265 |
Bailey , et al. |
April 23, 1991 |
**Please see images for:
( Certificate of Correction ) ** |
Packer for wellhead repair unit
Abstract
A geothermal wellhead repair unit including a mechanically set
packer to isolate the wellhead for removal and repair thereof. The
packer is run into the well string using a running tool. The packer
is set by placing tension on the mandrel to set the packing
elements and the slip assembly. Once the packer is set, the running
tool can be disengaged without fear of collapsing the packer and
the wellhead removed for repair or replacement. Upon replacement of
the wellhead, the running tool is used to unset and retrieve the
packer.
Inventors: |
Bailey; Thomas F. (Houston,
TX), Lancaster; Charles E. (Iola, TX), Lee; Richard
(The Woodlands, TX) |
Assignee: |
Drilex Systems, Inc. (Houston,
TX)
|
Family
ID: |
23598412 |
Appl.
No.: |
07/404,159 |
Filed: |
September 7, 1989 |
Current U.S.
Class: |
166/118; 166/123;
166/125 |
Current CPC
Class: |
E21B
19/086 (20130101); E21B 23/06 (20130101); E21B
33/1292 (20130101); E21B 33/1294 (20130101) |
Current International
Class: |
E21B
19/086 (20060101); E21B 23/00 (20060101); E21B
23/06 (20060101); E21B 33/129 (20060101); E21B
33/12 (20060101); E21B 19/00 (20060101); E21B
023/06 (); E21B 033/12 () |
Field of
Search: |
;166/118,123,125,131,133,138,140 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kisliuk; Bruce M.
Attorney, Agent or Firm: Zarins; Edgar A. Sutherland;
Malcolm L.
Claims
I claim:
1. A well packer mechanically settable and retrievable within a
well bore using a running tool to selectively isolate the wellhead,
said packer comprising:
an inner mandrel;
a sleeve assembly movably mounted to said inner mandrel, said
sleeve assembly selectively adjustable along said mandrel for
longitudinal movement of said mandrel in a first direction relative
to said sleeve assembly to set said packer; and
locking ratchet means for selectively preventing longitudinal
movement of said mandrel in a second direction relative to said
sleeve assembly thereby preventing release of said packer, said
locking ratchet means including a first ratchet nut movable to a
preset position as said packer is run into the well bore and a
second ratchet nut said ratchet means being selectively
disengageable to allow longitudinal movement of said mandrel in
said second direction relative to said sleeve assembly to unset
said packer for retrieval thereof;
said sleeve assembly including at least one packing element
selectively compressible into sealing engagement with the well bore
and at least one slip selectively engageable with the well bore to
set said packer within the well bore.
2. The packer as defined in claim 1 and further comprising a
release/tie back sleeve detachably connected to an upper end of
said mandrel by latching means, said release/tie back sleeve
attached to the running tool and selectively detachable from said
mandrel whereby tension on the running tool will be transmitted to
said mandrel to set said packer and said release/tie back sleeve is
reconnectably detachable from said mandrel to leave said set packer
within the well bore.
3. The packer as defined in claim 2 wherein said locking ratchet
means includes a ratchet surface formed on said inner mandrel and
said first ratchet nut disengagably connected to said sleeve
assembly, said ratchet surface and said ratchet nut having
cooperating helical ratchet surfaces which permit longitudinal
movement in said first direction while preventing longitudinal
movement in said second direction, said ratchet surfaces engaging
as said packer is run into the well bore to preset said packer,
said ratchet surfaces cooperating to facilitate setting of said
packer upon application of upward tension on said mandrel.
4. The packer as defined in claim 3 wherein said ratchet sleeve and
first ratchet nut are threadably disengageable whereby said locking
ratchet means may be rotatably released to allow longitudinal
movement of said sleeve assembly in said second direction relative
to said mandrel to unset said packer for retrieval.
5. The packer as defined in claim 3 wherein said ratchet means is
detachably connected to said sleeve assembly whereby said sleeve
assembly may be disconnected from said ratchet means to unset said
packer for retrieval.
6. The packer as defined in claim 2 wherein said mandrel includes a
partial axial passageway in fluid communication with an equalizing
port.
7. The packer as defined in claim 6 wherein said release/tie back
sleeve includes a lateral port selectively alignable with said
equalizing port of said mandrel to provide fluid pressure
equalization above and below said packer.
8. The packer as defined in claim 7 wherein said release/tie back
sleeve is selectively connected to said mandrel by a J-slot
assembly.
9. The packer as defined in claim 1 wherein said sleeve assembly
includes at least one drag block to facilitate setting of said at
least one packing element and said at least one slip.
10. A well packer settable and retrievable within a well bore using
a running tool to selectively isolate the wellhead of a well for
removal of the wellhead valve, said packer comprising:
an inner mandrel;
a release/tie back sleeve detachably connected to an upper end of
said mandrel, the running tool secured to said sleeve for running
and retrieving said packer from the well bore;
a sleeve assembly movably mounted to said inner mandrel, said
sleeve assembly including at least one packing element selectively
compressible into sealing engagement with the well bore and at
least one slip selectively engageable with the well bore, said
sleeve assembly selectively adjustable along said mandrel for
longitudinal movement of said mandrel in a first direction relative
to said sleeve assembly to set said at least one packing element
and said at least one slip; and
locking ratchet means to selectively prevent longitudinal movement
of said mandrel in a second direction relative to said sleeve
assembly unsetting said packer, said ratchet means including a
first ratchet nut moving from a release position to a preset
position as said packer is run into the well bore to facilitate
setting of said packer and a second ratchet nut to facilitate
selective release of said ratchet means to allow longitudinal
movement of said mandrel in said second direction relative to said
sleeve assembly to unset said at least one packing element and said
at least one slip for retrieval of said packer;
said release/tie back sleeve detachable from said mandrel to leave
said set packer within the well bore and reconnectable to said
mandrel to unset and retrieve said packer.
11. The packer as defined in claim 10 wherein said sleeve assembly
includes at least one drag block engageable with the well bore to
facilitate setting of said at least one packer element and said at
least one slip.
12. The packer as defined in claim 10 wherein said locking ratchet
means includes a ratchet surface formed on said inner mandrel and
said first ratchet nut connected to said sleeve assembly, said
ratchet surface and said first ratchet nut having cooperating
ratchet surfaces which permit relative longitudinal movement in
said first direction to set said packer while preventing relative
longitudinal movement in said second direction to release said
packer, said first ratchet nut engaging said ratchet surface as
said packer is run into the well bore to preset said packer such
that upward tension applied to said mandrel will set said packer
within the well bore.
13. The packer as defined in claim 12 wherein said ratchet nut
includes shear means for releasing said ratchet nut from said
sleeve assembly such that said mandrel and ratchet nut may move
longitudinally in said second direction relative to said sleeve
assembly to release said packer for retrieval from the well
bore.
14. The packer as defined in claim 12 wherein said ratchet nut
threadably engages said ratchet surface such that said locking
ratchet means may be rotatably released to allow longitudinal
movement of said mandrel in said second direction relative to said
sleeve assembly to unset said packer.
15. The packer as defined in claim 10 wherein said inner mandrel
includes a partial axial bore open to the bottom of said packer and
a selectively closable lateral port formed through said mandrel to
provide selective fluid communication between said partial axial
bore and the well bore above said sleeve assembly, said lateral
port and partial axial bore forming a selectively openable
equalizing fluid passageway.
16. A well packer mechanically settable and retrievable within a
well bore using a running tool to selectively isolate the wellhead,
said packer comprising:
an inner mandrel;
an outer sleeve assembly mounted to said inner mandrel, said outer
sleeve assembly including slip means and packing means selectively
engageable with the well bore upon movement of said mandrel in a
first direction relative to said sleeve assembly to set said
packer;
locking ratchet means to selectively prevent longitudinal movement
of said mandrel, said outer sleeve assembly including slip means
and packing means selectively engageable with the well bore upon
movement of said mandrel in a first direction relative to said
sleeve assembly to set said packer,
locking ratchet means to selectively prevent longitudinal movement
of said mandrel in a second direction relative to said outer sleeve
assembly to unset said packer, said ratchet means being selectively
disengageable to allow longitudinal movement of said mandrel in
said second direction relative to said outer sleeve assembly to
unset said packer for retrieval, said ratchet means including a
first ratchet nut and a second ratchet nut connected to said outer
sleeve assembly, said first ratchet nut selectively engageable with
a ratchet surface formed on said mandrel and said second ratchet
nut selectively cooperating with a ratchet sleeve slidably mounted
to said mandrel;
said first ratchet nut cooperating with said ratchet surface as
said packer is run into the well bore to preset said packer such
that upward tension applied to said mandrel will set said slip
means and packing means of said outer sleeve assembly and said
second ratchet nut adjustably engaging said ratchet sleeve to
facilitate release of said ratchet means for retrieval of said
packer; and
a release/tie back sleeve detachably connected to an upper end of
said mandrel, the running tool secured to said release/tie back
sleeve for running and retrieving said packer from the well bore,
said release/tie back sleeve detachably connected to said mandrel
by a J-slot assembly.
17. The packer as defined in claim 16 wherein said mandrel includes
a partial axial bore open to the bottom of said packer and a
selectively closable lateral port formed in said mandrel to provide
selective fluid communication between said partial axial bore and
the well bore above said packer, said lateral port closable and
openable upon detachment and attachment of said release/tie back
sleeve respectively.
18. The packer as defined in claim 16 wherein said ratchet nut
includes shear means for releasably connecting said ratchet nut to
said outer sleeve assembly such that said mandrel and ratchet nut
may move longitudinally in said second direction relative to said
sleeve assembly to release said packer for retrieval from the well
bore.
19. The packer as defined in claim 16 wherein said ratchet nut
threadably disengages said ratchet surface such that said ratchet
locking means may be rotatably released by rotating said mandrel
and ratchet surface relative to said ratchet nut and outer sleeve
assembly to allow longitudinal movement of said mandrel in said
second direction relative to said sleeve assembly to release said
packer for retrieval from the well bore.
20. The packer as defined in claim 16 wherein said outer sleeve
assembly includes at least one drag block engageable with the well
bore to facilitate setting of said slip means and packing
means.
21. The packer as defined in claim 16 and further comprising a
shear bolt connecting said release/tie back sleeve to said upper
end of said mandrel, said bolt shearing prior to disconnection of
said J-slot assembly.
22. A packer mechanically settable and retrievable within a well
bore using a running tool to selectively isolate a section of the
well bore, said packer comprising:
an inner mandrel;
a sleeve assembly having packing means mounted to said inner
mandrel, said sleeve assembly selectively adjustable along said
mandrel for longitudinal movement of said mandrel in a first
direction relative to said sleeve assembly to set said packer;
and
locking ratchet means for selectively preventing longitudinal
movement of said mandrel in a second direction relative to said
sleeve assembly thereby preventing release of said packer, said
locking ratchet means including a first ratchet nut and a second
ratchet nut connected to said sleeve assembly and a ratchet surface
formed on said mandrel;
said locking ratchet means selectively movable between a released
position wherein said first ratchet nut is disengaged from said
ratchet surface and a preset position wherein said first ratchet
nut engages said ratchet surface of said mandrel as said packer is
run into the well bore such that subsequent upward tension on said
mandrel will set said packing means preventing longitudinal
movement of said mandrel in said second direction to prevent
release of said packer, said second ratchet nut adjustably engaging
a ratchet sleeve slidably mounted to said mandrel to facilitate
release of said ratchet means for retrieval of said packer.
23. The packer as defined in claim 22 wherein said first ratchet
nut threadably disengages said ratchet surface such that said
locking ratchet means may be rotatably released by rotating said
mandrel and ratchet surface relative to said ratchet nut and sleeve
assembly thereby allowing longitudinal movement of said mandrel in
said second direction relative to said sleeve assembly to release
said packer for retrieval from the well bore.
24. The packer as defined in claim 22 wherein said ratchet means
includes shear means for releasably connecting said ratchet nut to
said sleeve assembly such that said mandrel and ratchet nut may
move longitudinally in said second direction relative to said
sleeve assembly to release said packer for retrieval from the well
bore.
Description
BACKGROUND OF THE INVENTION
I. Field of the Invention
This invention relates to a unit for isolating a wellhead for
removal and repair of the wellhead and, in particular, to a packer
for a wellhead repair unit which securely packs off the well to
permit safe removal of the wellhead and which subsequently can be
retrieved mechanically to allow continued production.
II. Description of the Prior Art
Various devices have been developed to isolate a well for removal
and repair of the wellhead in a geothermal well. The extreme
temperatures and pressures found in geothermal wells makes it
important to safely seal off the well prior to removal of the
wellhead. The prior known repair systems utilize a hydraulically
set packer which is dependent upon the pressure balance between the
downhole pressure and the hydraulic pressure applied through the
running tool from the surface. Some tools include means for
increasing the gripping action within the casing in the event
downhole pressure increases. To release the packer once the repairs
are completed and the wellhead is replaced, the hydraulic pressure
is increased to overcome the downhole pressure.
Because the past known repair units are dependent upon a critical
pressure balance, variations in the downhole pressure can cause
release and travel of the packer or in the extreme case a blowout
of the tool. Pressure variations may also cause the hydraulically
set packer to slip down into the casing. As a result, because the
retrieval tool has limited downhole reach, re-engagement may not be
possible requiring other fishing techniques or lost production.
Alternatively, an increase in downhole pressure can cause the
packer to form a harder grip with the casing wall requiring an
increased hydraulic pressure to release the packer.
Other packers are well known for a variety of applications.
However, not all packers are suitable for the environment of a
geothermal well. Moreover, many packers are not retrievable and are
merely drilled out when further work is needed on the well. These
are not suitable alternatives for a completed and operated
geothermal well.
SUMMARY OF THE PRESENT INVENTION
This invention overcomes the disadvantages of the prior known
geothermal wellhead repair units by providing a mechanically set
and released packer for the repair unit which securely packs-off
the geothermal well to facilitate removal and repair of the
wellhead.
The geothermal wellhead repair unit of the present invention
generally comprises a hydraulic extension assembly attachable to
the top flange of the wellhead valve, a running tool extending
through an upper seal assembly and connected to a well packer. The
hydraulic extension assembly includes hydraulic cylinders for the
controlled insertion and retraction of the running tool and packer
to the desired position within the casing. The packer includes a
plurality of packing elements separated by packing spacers, a slip
assembly for selective engagement with the casing wall, and a set
of, drag blocks to facilitate setting of the tool. The setting
assemblies are disposed within an outer sleeve concentrically
mounted to an inner mandrel having a pressure equalizing passageway
formed therein. A J-slot connector is used at the upper end to
facilitate disconnection and connection of the running string from
the packer. The lower end of the packing tool includes a ratchet
thread assembly which controls the selective setting and release of
the packer and connects the outer sleeve assembly to the inner
mandrel. The packer is provided with at least two means for release
to ensure retrieval of the tool for further production.
The packer is set through mechanical longitudinal movement of the
mandrel relative to the outer sleeve assembly. As the tool is run
into the hole, the frictional engagement of the drag blocks with
the casing will cause the tool to be pre-loaded as a bottom ratchet
nut engages a ratchet sleeve. Once the packer is positioned, the
mandrel is drawn upwardly against the friction of the drag blocks
causing the slip assembly and packing elements to be set against
the casing. With the packer set in the casing, the running tool can
be disconnected through disconnection of the release/tie back
sleeve from the upper end of the packer which will also cause the
pressure equalizing passageway to be closed. With the required
repairs completed, the release/tie back sleeve is reconnected to
the packer thereby opening the equalizing passageway. The primary
and preferred method of releasing the packer is by rotating the
mandrel relative to the outer sleeve assembly to threadably
disconnect the ratchet nut from the ratchet sleeve resulting in
release of the packer. Other methods of release involve shear pins
and added longitudinal force to release the connection between the
outer sleeve assembly and the mandrel. With the packer unset, the
tool can be removed from the hole for further production.
Other objects, features and advantages of the invention will be
apparent from the following detailed description taken in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWING
The present invention will be more fully understood by reference to
the following detailed description of a preferred embodiment of the
present invention when read in conjunction with the accompanying
drawing in which like reference characters refer to like parts
throughout the views and in which:
FIG. 1 is a perspective view of a wellhead repair unit embodying,
the retrievable packer of the present invention to a wellhead of a
well bore;
FIG. 2 is a perspective view of the present invention with the
packet being run into the well bore;
FIG. 3 is an enlarged perspective partially in cross-section of the
packer prior to being run into the well bore;
FIG. 4 is an enlarged perspective partially in cross-section the
packer being run into the well bore;
FIG. 5 is an enlarged perspective partially in cross-section the
packer set in the well bore;
FIG. 6 is a partial cross-sectional view of the released packet
unset by a first method; and
FIG. 7 is a partial cross-sectional view of the packer unset by a
second method.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT
INVENTION
Referring first to FIGS. 1 and 2, there is shown an apparatus 10
for isolating a wellhead 12 of a well bore 14 for removal and
repair of the wellhead 12. The repair unit 10 includes a packer 16
embodying the present invention for packing off the well bore 14 to
permit safe removal of the well head 12. The unit 10 is mountable
to the wellhead 12 and includes a hydraulic extension assembly 18
which connects to a running string 20 detachably secured to the
packer 16. The hydraulic extension assembly 18 controls the raising
and lowering of the running string 20 in order to run and retrieve
the packer 16 within the well bore 14. As will be subsequently
described in greater detail, the packer 16 is run into the well
bore 14 using the hydraulic extension assembly 18, mechanically set
in the well 14, and detached from the running string 20 to allow
removal and repair of the wellhead 12. Once repairs are completed,
the unit 10 is again attached to the wellhead 12 and the running
string 20 is lowered to retrieve the packer 16 for continued
production. The packer 16 of the present invention allows
mechanical setting and retrieval of the packer 16 while ensuring a
secure pack-off of the well bore 4.
Referring now to FIGS. 3 through 5, FIG. 3 shows the packer 16
hanging freely prior to being run into the well bore 14, FIG. 4
shows the packer 16 as it is run into the well bore 14, and FIG. 5
shows the packer 16 set within the well bore 14. The packer 16 of
the present invention generally comprises an inner mandrel 22
having a partial axial bore 24, outer sleeve assembly 26 which
carries the setting components of the packer 16 and is
longitudinally movable relative to the mandrel 22, and a connector
assembly 28 which detachably connects the packer 16 to the running
string 20. The packer 16 is mechanically set by applying tension to
the mandrel 22 relative to the sleeve assembly 26 to set the
components thereof and thereafter released by rotating the mandrel
22 relative to the sleeve assembly 26 as will be subsequently
described. A secondary method of release can be accomplished by
applying added tension to the mandrel 22 in the event rotation does
not release the tool.
The outer sleeve assembly 26 includes a set of drag blocks 30 which
are spring-biased outwardly to engage the casing wall 14 and
provide an initial tension to the packer 16. Positioned within the
sleeve assembly 26 just downhole the drag blocks 30 are slip
assemblies 32 selectively engageable with the wall 14 as the packer
16 is set to securely position the packer 16. The slip assemblies
32 preferably include slip elements 34 which have wall engaging
teeth and upper slip cone 36 and lower slip cone 38 to drive the
slip elements 34 outwardly into engagement with the wall 14. The
slip elements 34 are retained by slip body 40. The slip elements 34
are driven outwardly into engagement with the casing 14 as upper
slip cone 36 and lower slip cone 38 are drawn together beneath the
slip elements 34.
Spaced downhole of the slip assembly 32 is the sealing packer 42
comprising at least one packing element 44 selectively compressible
into sealing engagement with the well bore 14. The packing elements
44 are spaced apart by spacer rings 46 and are seated between an
upper packer sleeve 48 which extends beneath the packing elements
44 and spacer rings 46 to essentially carry the assembly and a
lower packer collar 50. The packing elements 44 and spacer rings 46
are slidably and sealingly engage the packer sleeve 48 to
facilitate packing compression. The elements 44 are compressed into
sealing engagement as the collar 50 shifts relative to the packer
sleeve 48. In order to limit relative movement between the collar
50 and sleeve 48, the sleeve 48 includes a groove 52 which receives
a slide screw 54.
Referring still to FIGS. 3-5, disposed primarily longitudinally
downhole of the packer assembly 42 is locking ratchet means 56
which selectively prevents movement of the outer sleeve assembly 26
relative to the mandrel 22 thereby locking the packer 16 in its set
position. Extending beneath the packer and slip assemblies in
sliding engagement with the mandrel 22 is a ratchet sleeve 58
having a ratchet surface 60 formed at the lower end thereof.
Similarly, the mandrel 22 includes a ratchet surface 62 formed
proximate the downhole end of the mandrel 22. Both ratchet surfaces
60 and 62 are helical in the form of threads to allow rotating
disengagement and permit longitudinal movement in only one
direction. A lower ratchet nut 64 is engageable with the ratchet
surface 62 of the mandrel 22 while an upper ratchet nut 66 is
engageable with the ratchet surface 60 of the ratchet sleeve 58.
The ratchet nuts 64 and 66 are connected to each other by a
mounting sleeve 68. The lower ratchet nut 64 is slidably secured to
the mounting sleeve 68 by a torque screw 70 received within a
longitudinal slot 72 of the sleeve 68. The upper ratchet nut 66 is
releasably secured to the mounting sleeve 68 by a first shear screw
74. The ratchet means 56 is housed within a housing sleeve 76. The
housing sleeve 76 is connected at its upper end to the lower packer
collar 50 and secured by set screw 78 and at its lower end to an
end sub 80 through threads 82. The housing sleeve 76 is also
detachably connected to the mounting sleeve 68 by second shear
screw 84. As tension is applied through the mandrel 22 to set the
packer 16, the ratchet surface 62 of the mandrel 22 will move
downwardly to engage the lower ratchet nut 64 thereby locking the
mandrel 22 against release relative to the ratchet means 56 and the
end sub 80. Furthermore, as the mandrel 22 travels downwardly, the
key block 33 will abut ratchet sleeve 58 preventing its movement
allowing the ratchet sleeve ratchet surface 60 to engage the upper
ratchet nut 66 thereby locking the ratchet sleeve 58 against
longitudinal movement relative to the upper ratchet nut 66. These
ratchet surfaces 60 and 62 and the inner surfaces of the ratchet
nuts 64 and 66 comprises angled cooperating teeth which allow them
to pass over each other in a first direction but prevent movement
in the opposite direction. The helical form of the ratchet surfaces
60 and 62 herein allow release by relative rotation of the
cooperating components. The lower ratchet nut 64 engages the
mandrel ratchet surface 62 as the packer 16 is run into the well
bore to preset the packer 16 prior to setting at the desired
location as will be subsequently described.
The end sub 80 includes a throughbore 86 which communicates with
the axial bore 24 of the mandrel 22. Formed at the upper end of the
axial bore 24 is a lateral port 88 which selectively communicates
with a port 90 in the connector assembly 28. The ports and bores
form a selectively closable fluid bypass passageway which
facilitates pressure equalization as the packer 16 is run into the
hole and prior to release and retrieval of the packer 16.
The connector assembly 28 includes a slide valve 92 mounted to the
mandrel 22 and having spaced apart seals 94. The port 90 is
preferably formed in the slide valve 92 and the seals 94 are spaced
so as to seal off the lateral port 88 of the mandrel 22 as will be
subsequently described. Extending upwardly from the slide valve 92
are a plurality of connecting fingers 96. The fingers 96 detachably
connect the slide valve 92 to a release/tie back sleeve 98 and are
received within a recess 100 formed in the release/tie back sleeve
98. The mandrel 22 includes a similar recess 102 to receive the
fingers 96 when the slide valve 92 is drawn upwardly a
predetermined distance to allow disconnection of the release/tie
back sleeve 98 from the mandrel 22 and slide valve 92. The
release/tie back sleeve 98 is connected to the mandrel 22 by a
J-latch assembly 104. Additionally, the release/tie back sleeve 98
is detachably connected to the mandrel 22 by a tensile bolt 106
such that the sleeve 98 will release from the mandrel 22 only when
a predetermined amount of tension is applied to shear the bolt 106
ensuring that the packer 16 is set. The release/tie back sleeve 98
is connected to the running string 20 by threaded engagement.
Operation of the present invention provides mechanical setting and
release of the packer 16 including up to three alternative methods
of unsetting the packer 16 as will be subsequently described. Prior
to running into the well bore 14 (FIG. 3), the ratchet assembly 56
is disengaged and allowed to hang freely so long as the drag blocks
30 do not engage the casing wall 14. As the tool is run into the
hole using the running tool 20 and controlled by the hydraulic
extension system 18, the drag blocks 30 will engage the wall 14
placing a tension on the outer sleeve assembly 26. The frictional
engagement of the drag blocks 20 against the wall 14 will cause the
mandrel 22 to move downward faster than the outer sleeve assembly
26 and the ratchet sleeve 58 forcing the ratchet surface 62 of the
mandrel 22 into engagement with the lower ratchet nut 64
pre-setting the packer 16. In this position, the key block 33 will
abut the ratchet sleeve 58 as shown in FIG. 4 to prevent any
additional movement of the ratchet sleeve 58 relative to the
mandrel 22. At this point, any upward movement of the mandrel 22
will cause the packer 16 to set in the well bore 14 (FIG. 4)
although the packer 16 can be run downhole any necessary depth.
Once the packer 16 is positioned a sufficient depth within the well
bore 14, the packer 16 can be set by applying upward tension on the
mandrel 22 through the running string 20. Since the mandrel 22 is
now connected to the outer sleeve assembly 26 through the lower
ratchet nut 64 upward tension on the mandrel 22 will draw the outer
sleeve assembly 26 against the frictional engagement of the drag
blocks 30. As upward tension is applied, the force will be
conducted through the lower ratchet nut 64, the mounting sleeve 68,
and housing sleeve 76 against the lower collar 50 causing initial
compression of the packing elements 44 against the packing sleeve
48. Continued tension will cause lower slip cone 38 to move towards
upper slip cone 36 forcing the slip elements 34 outwardly into
engagement with the casing wall 14. With the slip assembly 32 set,
continued tension will cause full compression of the packing
elements 44 into sealing engagement with the wall 14 as shown in
FIG. 5. The tension will also be transferred from the lower ratchet
nut 64 through the mounting sleeve 68 to the upper ratchet nut 66.
Since the ratchet sleeve 58 engages the key block 33 at its upper
end continued tension will cause the upper ratchet nut 66 to travel
along the ratchet surface of the ratchet sleeve 58. Although this
movement will be minimal it ensures secure setting of the packer 16
by preventing release between the mandrel 22 and ratchet sleeve 58
and the upper ratchet nut 66. Moreover, since the mounting sleeve
68 is tied to the outer sleeve 26 by shear screw 84 shearing of the
screw 84 allows the packing elements 44 to relax relative to the
mandrel 22, ratchet sleeve 58 and ratchet means 56. Thus, the
ratchet means 56 shifts between an unset position prior to being
run into the well bore (FIG. 3), a preset position as the packer 16
is run into the well (FIG. 4), a set position (FIG. 5) and either
of the release modes (FIGS. 6 and 7).
With the packer 16 set within the well bore 14, additional upward
tension will cause the tensile bolt 106 to break allowing the
release/tie back sleeve 98 to separate from the mandrel 22. As this
occurs, the upward movement of the sleeve 98 will draw the slide
valve 92 upwardly until fingers 96 seat within the recess 102 of
the mandrel 22. The upward movement of the slide valve 92 will have
closed the lateral port 88 of the mandrel 22 by positioning the
seals 94 an opposite side thereof closing the bypass passageway.
The release/tie back sleeve 98 can now be disconnected from the
packer 16 by disconnecting the J-latch 104 and the running string
20 and sleeve 98 removed from the well bore 14 to permit work on
the wellhead 12.
Once repairs have been completed, the release/tie back sleeve 98 is
run into the hole on the string 20 into engagement with the packer
16. As the release/tie back sleeve 98 re-engages, the slide valve
92 will be forced downwardly to align the ports 88 and 90
equalizing the pressure above and below the packer 16. With the
running string 20 reattached the packer 16 can now be mechanically
unset and retrieved. The preferred method of unsetting is to rotate
the running string 20 and mandrel 22 relative to the outer sleeve
assembly 26. This will cause the thread-like ratchets 62 of the
mandrel 22 and the lower ratchet nut 64 to threadably disconnect
releasing the sleeve assembly 26. Upon release the packer 16 will
return to its unset position shown in FIG. 3 releasing the packer
assembly 42 and the slip assembly 32 from engagement with the well
bore 14. Since the ratchet surfaces have not been preset through
downward movement, the packer 16 can be retrieved without
resetting.
Since release of the packer 16 occurs when the mandrel 22 is
released from the outer sleeve assembly 26, the packer 16 can be
unset by applying additional upward tension on the mandrel 22 until
the second screw 84 shears freeing the housing sleeve 76, which is
secured to the outer sleeve assembly 26, from the ratchet mechanism
56 and the mandrel 22 as shown in FIG. 7. A still further
alternative combines shear force with threaded disengagement.
Sufficient force is applied to shear screw 74 of the upper ratchet
nut 66 and thereafter the upper ratchet nut is threadably
disconnected from the ratchet surface 60 of the sleeve 58 releasing
the packer 16.
Thus, the present invention provides a mechanically set and unset
packer 16 for use in a wellhead repair unit which ensures sealing
pack-off of the well while also allowing for simple retrieval of
the packer 16.
The foregoing detailed description has been given for clearness of
understanding only and no unnecessary limitations should be
understood therefrom as some modifications will be obvious to those
skilled in the art without departing from the scope and spirit of
the appended claims.
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